phpunit4 Starter Project for PHP 5.3 Environment - only version 4 is available in this limited dev environment.
https://phpunit.de/getting-started/phpunit-4.html
$ composer require --dev phpunit/phpunit ^4
$ vendor/phpunit/phpunit/phpunit ./tests
Should work just like this ;)
PHPUnit 4.8.36 by Sebastian Bergmann and contributors.
.
Time: 329 ms, Memory: 7.00MB
OK (1 test, 1 assertion)